Mercury Stable Isotope Fractionation during Abiotic Dark Oxidation in the Presence of Thiols and Natural Organic Matter

• DOI: 10.1021/acs.est.8b05047
• Publication Date: 2018-10-29T13:49:20Z
• Authors: Wang Zheng; Jason D. Demers; Xia Lu; Bridget A. Bergquist; Ariel D. Anbar; Joel D. Blum; Baohua Gu
• Keywords: Mercury; Natural Organic Matter; Methylmercury; Mass-independent fractionation

Mercury (Hg) stable isotope fractionation has been widely used to trace Hg sources and transformations in the environment, although many important processes remain unknown. Here, we describe during abiotic dark oxidation of dissolved elemental Hg(0) presence thiol compounds natural humic acid. We observe equilibrium mass-dependent (MDF) with enrichment heavier isotopes oxidized Hg(II) a small negative mass-independent (MIF) owing nuclear volume effects. The measured factors for MDF MIF (ε202Hg E199Hg) ranged from 1.10‰ 1.56‰ -0.16‰ -0.18‰, respectively, agreed well theoretically predicted values between thiol-bound Hg(II). suggest that observed was likely controlled by exchange following production Hg(II)-thiol complex. However, significantly attenuated initial stage acid attributed kinetic effect (KIE). This research provides additional experimental constraints on interpreting signatures implications use as tracer biogeochemical cycle.